This invention relates generally to the determination of gas in well drilling mud, before the circulating mud reaches the surface drilling site; more particularly the invention concerns the provision of method and apparatus to determine the gas content of a mud sample through pressure sensing before and after the volume of the sample is increased.
For some time, when drilling subsea, there has been a need for an early warning system to determine the presence of gas in the mud before it reaches the surface, the purpose being to warn the drilling crew of the presence of gas in the mud while it is in the vicinity of the wellhead, rather than wait until that mud has reached the surface. Such a warning would give the crew considerable extra time to secure the well, start to heavy up the mud, and to circulate out any gas cut mud. Unless appropriate steps are taken, the well can blow out, endangering the lives of the crew members, to say nothing of great loss of oil or gas, and damage to the drilling rig.